Several different input mechanisms for performing operations on an electronic device are available today. In particular, touch devices, such as touch screens, are becoming increasingly popular in portable electronic devices because of their ease and versatility of operation. Touch devices allow a user to make selections or move objects on the screen by simply moving their finger or a stylus on a touch panel.
Among several types of technologies for implementing a touch device, capacitive touch sensing devices work particularly well in portable electronic devices. In a capacitive touch device, as an object such as a finger approaches the touch panel, a tiny capacitance can form between the object and the sensing points in close proximity to the object. By detecting changes in capacitance, the sensing circuit can recognize the object and determine the location of the object on the touch panel.
In addition to detecting the location of the object, the pressure of the object may also be detected in order to provide more functionality to the touch device. For example, different force applied on the same sensing point may correspond to different actions performed by the touch device. Therefore, it is an important subject in the industry to design a method for hybrid touch sensing, for detecting a normal touch (corresponding to the position coordinate of the object on the touch panel) and a force touch (corresponding to the vertical pressure applied to the touch panel).